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mindebtpayoff.go
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mindebtpayoff.go
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package finance
import (
"fmt"
"math"
"strconv"
"time"
"github.com/rsingla/learngo/pkg/model"
)
func MinPayoff(d model.Debt) []model.Payment {
budget := d.MonthlyBudget
trades := d.Tradelines
var month int = 0
balMap := make(map[string]float64)
for _, trade := range trades {
balMap[trade.ID] = trade.Balance
}
zeroMap := make(map[string]float64)
amortization := []model.Payment{}
for month <= 600 {
myDate := addMonthsToGetYear(month)
year := myDate.Year()
monthly_days := daysIn(month, year)
days := daysInAfterMonth(month)
pays := []model.MonthlyPayment{}
monthDate := strconv.Itoa(myDate.Year()) + " " + myDate.Month().String()
totalInterest := 0.0
totalPrincipal := 0.0
totalPayment := 0.0
for _, trade := range trades {
balance := balMap[trade.ID]
if balance <= 0.0 {
continue
}
dailyRate := trade.InterestRate / float64(days*100)
minPayment := float64(trade.MinimumPayment)
monthlyPay := minimumPayment(dailyRate, monthly_days, minPayment, month, budget, balance, trade.ID)
balMap[trade.ID] = monthlyPay.RemainingBalance
pays = append(pays, monthlyPay)
if balMap[trade.ID] == 0 {
zeroMap[trade.ID] = 0.00
}
totalInterest += monthlyPay.Interest
totalPrincipal += monthlyPay.PrincipalPayment
totalPayment += (monthlyPay.Interest + monthlyPay.PrincipalPayment)
}
payment := model.Payment{
Month: monthDate,
TotalPayment: totalPayment,
TotalPrincipalPayment: totalPrincipal,
TotalInterest: totalInterest,
MonthlyPayments: pays}
amortization = append(amortization, payment)
if len(zeroMap) == len(balMap) {
break
}
month++
}
fmt.Println("Total Time : ", month, amortization)
return amortization
}
//A = P * (r(1+r)^n)/ ((1+r)^n - 1)
func minimumPayment(dailyRate float64, monthly_days int, minPayment float64, month int, budget int, balance float64, id string) model.MonthlyPayment {
interestPayment := balance * dailyRate * float64(monthly_days)
principalPayment := minPayment - interestPayment
if balance < minPayment {
principalPayment = balance
}
balance = balance - principalPayment
monthlyPay := model.MonthlyPayment{ID: id, Month: month, Interest: interestPayment, PrincipalPayment: principalPayment, RemainingBalance: balance}
fmt.Println(monthlyPay)
return monthlyPay
}
func currMonth() time.Month {
currentTime := time.Now()
return currentTime.Month()
}
func daysIn(monthsAfter int, year int) int {
myDate := time.Now().AddDate(0, monthsAfter, 0)
return time.Date(year, myDate.Month(), 0, 0, 0, 0, 0, time.UTC).Day()
}
func daysInAfterMonth(monthsAfter int) int {
myDate := time.Now().AddDate(0, monthsAfter, 0)
myDateInYear := time.Now().AddDate(1, monthsAfter, 0)
diff := (myDateInYear.Sub(myDate).Hours() / 24)
return int(diff)
}
func addMonthsToGetYear(monthsAfter int) time.Time {
myDate := time.Now().AddDate(0, monthsAfter, 0)
return myDate
}
func daysInYear(year int) int {
// This is equivalent to time.daysIn(m, year).
days := time.Date(year, time.December, 31, 0, 0, 0, 0, time.UTC).YearDay()
return days
}
//N = (-log(1- r * A / P)) / log (1 + r)
// r is yearly Rate interest, A is total balance, P is payment
func payoffTime(rate float64, trade model.Tradeline) float64 {
balance := float64(trade.Balance)
minPayment := float64(trade.MinimumPayment)
yearlyRate := rate / (12 * 100)
payoffNumerator := -1 * math.Log(1-yearlyRate*balance/minPayment)
payoffTimeDenominator := math.Log(1 + yearlyRate)
payoffTime := payoffNumerator / payoffTimeDenominator
return payoffTime
}